For the vegetables: In a large nonstick skillet, heat the oil over medium-high heat. Add the garlic, onions, peppers, herbes de Provence, salt and pepper. Cook, stirring occasionally, until the vegetables are soft, 8 to 10 minutes. Remove the vegetables and set aside.
For the steak: In the same skillet, heat the oil over high heat. Add the steak and sprinkle with the salt and pepper. Cook, stirring constantly, until the steak is cooked through to desired doneness, 2 to 3 minutes.
For the panini: Spoon 2 tablespoons of marinara sauce onto the bottom of each roll. Add the arugula and top with the cooked vegetables. Arrange the steak on the vegetables and place a slice of cheese on top. Place the tops on the rolls and cook in a panini maker until the cheese has melted, about 5 minutes.